In the second study, 67 percent steered more accurately. "Especially in the areas where there were curves and turns, when they were using the headset, they were much more accurate," she said.

Johnson's comments might be taken with a grain of salt because Plantronics manufactures some of those headsets. But the U. study found that drivers who talked on cell phones were 18 percent slower in braking and took 17 percent longer to regain the speed they lost when they braked.

"It's not specifically correct, but the rule of thumb is, if you take someone's eyes off the road, it has 10 times more impact than a lot of other distractions," Gardner said. "If those eyes are off the road, you can't drive."

That's where dashboard displays come in handy. Ditto for putting radio buttons on the steering wheel rather than elsewhere.

"It's amazing how much you cue in when you drive, listening," he said. "You can hear people. You can hear a car driving up to the intersection, even with your windows up. And without realizing it or not, you're cuing off that. So a conversation or a child screaming in the background or a cell phone call could have an effect on that. . . . You take the hand off the wheel, you can't drive, so putting those buttons placed on the steering wheel to work with is great."

Because they're distracted, and because people filter out a lot of information, they likely never realize there is a problem with their concentration, he said.

"That's what's happening when you're looking for the street sign in a place you haven't driven before and you miss the stop light. That's what happens with your CE device that you haven't used before, and you've missed it. And you don't know that's going on," Gardner said.

Avoid distraction

The experts acknowledged a fine line between eliminating a distraction and causing a new one. Kanianthra mentioned that a series of alert systems — to announce potential forward or intersection collisions, among others — have been developed.

Peter Roessger, senior manager of business development, human factors for Harman/Becker Automotive Systems GmbH, discussed how at least one new device will feature radio, navigation systems, telephone service, online content, e-mail capability, an address book and play MP3 files and CDs, but it will have scrolling and push-button interfaces that will make it simple to use even while driving. Gardner spoke of navigation systems that provide spoken directions instead of forcing a driver to fumble with buttons and confusing maps.

"It's about getting the right information at the right time in the right way," Gardner said.